Transimpedance amplifier assembly with separate ground leads and separate power leads for included circuits

ABSTRACT

The optoelectronic device includes a photo diode and an amplifier, which amplifies output of the photo diode. The amplifier includes an input stage and an output stage. In one embodiment, the input stage has a series connection to a resistor, which is connected to a ground. The output stage has a connection to ground that does not overlap the series connection. In another embodiment, the input stage has a first connection to a bypass capacitor, which is connected to a power source. The output stage has a separate, second connection to the capacitor, which prevents high frequencies from flowing between the input stage and said output stage via a connection to the power source.

[0001] The present application claims priority, under 35 U.S.C. 119(e),to a U.S. Provisional Patent Application bearing serial No. 60/366,089,filed Mar. 19, 2002, which is incorporated herein by reference.

BRIEF DESCRIPTION OF THE INVENTION

[0002] The present invention relates generally to optoelectronicdevices, and particularly to a circuit interconnect for controlledimpedance at high frequencies.

BACKGROUND OF THE INVENTION

[0003] An optoelectronic device, such as a laser diode or a photo diode,is generally enclosed in a transistor outline (TO) package, whichprovides a conductive housing for the optoelectronic device. A laserdiode converts an electrical signal into an optical signal fortransmission over a fiber optic cable, while a photo diode converts anoptical signal into an electrical signal. In order for a laser diode toconvert an electrical signal into an optical signal, the electricalsignal must be sent through the TO package of the laser diode.Similarly, an electrical signal from a photo diode must be sent throughthe TO package of the photo diode to external electrical circuitry. Forhigh frequency operation, it is important to control the impedance seenby the electrical signals that flow into and out of the TO package.

[0004] TO package also include amplifiers to amplify the output of thephoto diode. Conventional amplifiers have common ground and powersignals for the various elements of the amplifier, which results in feedback gain and oscillations at high frequencies (e.g., above 5 GHz).

SUMMARY OF THE INVENTION

[0005] The present invention enables optoelectronic devices packaged intransistor outline (TO) packages to operate at high frequencies.

[0006] The optoelectronic device includes a photo diode and anamplifier, which amplifies output of the photo diode. The amplifierincludes an input stage and an output stage. In one embodiment, theinput stage has a series connection to a resistor, which is connected toa circuit ground. The output stage has a connection to circuit groundthat does not overlap the series connection. In another embodiment, theinput stage has a first connection to a capacitor, which is connected toground and a power source. The output stage has a second connection tothe capacitor, which prevents high frequencies from flowing between theinput stage and said output stage via a connection to the power source.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Additional objects and features of the invention will be morereadily apparent from the following detailed description and appendedclaims when taken in conjunction with the drawings, in which:

[0008]FIGS. 1 and 1A-1F are various diagrams of an optoelectronicassembly in accordance an embodiment of the invention.

[0009]FIG. 2 depicts the ground signal conductor side of a circuitinterconnect.

[0010]FIGS. 3A and 3B depict the back of a TO package in accordance withthe first and second embodiments.

[0011]FIG. 4 is a perspective view of a transmitter assembly inaccordance with an embodiment of the invention.

[0012]FIG. 5 is a front view of certain elements of a transmitterassembly in accordance with an alternate embodiment of the invention.

[0013]FIGS. 6A, 6B, 6C, and 6D are diagrams of a receiver assembly, andcomponents thereof, in accordance with embodiments of the invention.

[0014]FIG. 7 is a diagram of a transceiver assembly in accordance withan embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Referring to FIG. 1, there is shown an embodiment of anoptoelectronic assembly 100 in accordance with the present invention.The optoelectronic assembly may be a transmitter optoelectronic assemblyor a receiver optoelectronic assembly. The optoelectronic assemblyincludes an optoelectronic device or component having a housing that iscalled a transistor outline (TO) package 102. If the optoelectronicassembly is a transmitter optoelectronic assembly, the optoelectronicdevice is a light source such as a laser diode. If the optoelectronicassembly is a receiver optoelectronic assembly, the optoelectronicdevice is a detector such as a photo diode.

[0016] Signal contacts 112, also called signal leads, extend throughapertures in the base 124 of the TO package 102 and a circuitinterconnect 104. The signal contacts 112 are electrically connected tothe signal traces 114. The signal contacts 112 and the signal traces 114convey power and data signals between an external circuit 118 and thedevice or devices in the TO package 102.

[0017] Additionally, resistors 162 are preferably electrically connectedin series with the signal traces 114 and the signal contacts 112. Inpreferred embodiments, very short signal trace segments (not shown) aremechanically and electrically connected to the signal contacts 112. Theresistors 162 are then mechanically and electrically connected to theshort signal trace segments and the signal traces 114 by solder,conductive epoxy, or any other appropriate conductive attachmentmechanism. In other embodiments, the resistors are connected directly tothe signal contacts 112. Additionally, resistors 162 are generally notused for power connections between the external circuit 118 and the TOpackage 102. Finally, in some embodiments, the resistors 162 are used inthis way only for transmitter optoelectronic assemblies (as illustratedin FIG. 7).

[0018] The circuit interconnect 104 is preferably made of an elongatedpiece of flexible dielectric 120. The dielectric 120 serves as aninsulator between a ground signal conductor 116 on one side of thedielectric 120 and the resistors 162 and data signal traces 114 on theother side of the dielectric. The ground signal conductor 116 conveysground current between the external circuit 118 and the device ordevices in the TO package 102. While the embodiment shown in FIG. 1 hastwo signal contacts 112, resistors 162, and corresponding signal traces114, in other embodiments the number of signal contacts 112, resistors162, and signal traces 114 may be greater or fewer, depending on thenumber of power and data connections needed by the device or devicesinside the TO package 102.

[0019] Positioning the resistors 162 on the circuit interconnect 104 isan improvement over systems that include resistors inside the TO package102. As is known in the art, resistors dissipate heat. When a resistoris included inside the TO package 102 (e.g., a thin film resistordisposed on the submount 404 illustrated in FIG. 4), the resistor mayincrease the internal temperature of the TO package 102, which has anegative impact on the performance of the device or devices in TOpackage 102. Additionally, it is easier to replace resistors 162, ordynamically determine and then install appropriately sized resistors,after construction of the optoelectronic assembly when the resistors arepositioned on the circuit interconnect 104 instead of inside the TOpackage 102. The small size of the TO package makes replacement ofresistors in the TO package difficult. Using normal manufacturingtechniques, the TO package is sealed closed prior to operation of thelaser diode in the TO package, making replacement of any components inthe TO package, or requiring that manufacturing techniques be modifiedto enable dynamic sizing of the resistors in the TO package duringmanufacture of the optoelectronic component.

[0020] Embodiments that include a flexible dielectric 120 preferably usea flexible encapsulant 164 (e.g., a material known as “glob top”) tosecure the resistors 162 on the circuit interconnect 104. As illustratedin FIG. 1A, the flexible encapsulant 164 is deposited on top of theresistors 162, the portion of the circuit interconnect 104 immediatelysurrounding the resistors 162, and the signal traces 114. As a result,the resistors 162, the contact points between the resistors 162 and thesignal contacts 112, the contact points between the resistors 162, andthe signal traces 114 are fully covered by the flexible encapsulant 164.Typically, the flexible encapsulant 164 is deposited and cured to form abond with the circuit interconnect 104, the resistors 162, and thesignal traces 114. When the flexible dielectric 120 is flexed, theflexible encapsulant 164 holds the resistors 162 in place, thusrelieving stress that would otherwise be placed on the connectionsbetween the resistors 162 and the signal contacts 112 and on theconnections between the resistors and the signal traces 114. The presentinvention may be practiced using coverage patterns of the flexibleencapsulant 164 other than the particular pattern illustrated in FIG.1A.

[0021] Some embodiments of the invention that incorporate the use of theflexible encapsulant 164 also incorporate the use of anchor holes 166 inthe circuit interconnect 104 as illustrated in FIG. 1A. Both the frontand back sides of the anchor holes 166 are preferably completely coveredby the flexible encapsulant 164. The anchor holes 166 provide for a moresecure connection between the flexible encapsulant 164 and the circuitinterconnect 104. When applied to the circuit interconnect 104, theflexible encapsulant 164 flows through the anchor holes 166, whichprovide the flexible encapsulant 164 with edges to “grip” onto thecircuit interconnect 104. In the embodiment illustrated in FIG. 1A, twoanchor holes 166 are shown, but in alternate embodiments, a larger orsmall number of anchor holes 166 are used. The invention, moreover, isnot limited to the specific positioning of the anchor holes 166illustrated in FIG. 1A. so long as other elements (e.g., signal traces114) on the circuit interconnect 104 are avoided.

[0022] The external, back surface of the base 124 (of the TO package) issometimes called the “ground plate,” because the base 124 of the TOpackage is grounded by a connection between the ground plate and theground conductor 116 on the circuit interconnect 104. The groundconnection to the base 124 provides a circuit ground voltage source andground current connection for the electrical and optoelectroniccomponents in the TO package 102.

[0023] To avoid signal reflections and other signal degradations, theimpedance of the signal path from the device or devices in the TOpackage 102 to the external circuit 118 must be kept as consistent aspossible. The characteristic impedance (also called the transmissionline impedance) of the signal traces 114 is precisely determined by thethickness of the dielectric and the width of the data signal traces 114.This characteristic impedance is preferably set so that for signals in apredefined frequency range (e.g., 20 kHz-10 GHz), the characteristicimpedance of the signal traces approximately matches the impedance ofthe external circuit 118 and also approximately matches the impedance ofthe device or devices in the TO package 102 as measured from the pointof connection between of the signal traces 114 and the resistors 162(and thus includes the impedances of the resistors 162, signal contracts112, bond wires in the TO package, and so on).

[0024] As used in this document, two impedances are defined to“approximately match” when the two impedances are either exactly thesame or one of the impedances is larger than the other, but no more than50% larger. In other words, the impedance of the signal traces 114 arewithin a factor of about 1.5 of the impedance of the external circuit118 and are also within a factor of about 1.5 of the impedance of thedevice or devices in the TO package 102 (including the impedance of theresistors 162, signal contacts 112 and bond wires in the TO package).Preferably the impedance of the signal traces 114 is within 25% (i.e.,within a factor of about 1.25) of the impedances of the external circuit118 and the device or devices in the TO package 102. When the device inthe TO package is a transmitter, the impedance of the signal traces 114is typically between 20 and 30 ohms, and the impedance of each of theresistors 162 is approximately 18 ohms. Note that transmitter devicestypically included in the TO package 102 (e.g., a laser diode) and thesignal contacts 112 are generally low impedance devices. As a result,the resistors 162 are the primary means of approximately matching theimpedance of the device or devices in the TO package 102, as measuredfrom the point of connection between the signal traces 114 and theresistors 162, to the impedance of the signal traces 114. When thedevice in the TO package 102 is a receiver (e.g. photo diode), theimpedance of the signal traces 114 is typically 50 ohms and, typically,no resistors 162 are used. However, in other embodiments, resistors 162may be used in conjunction with a receiver device in the TO package 102.

[0025] In a preferred embodiment the circuit interconnect 104 has athickness between 0.003 and 0.012 inches, and the dielectric substrate120 of the circuit interconnect is preferably polyimide or polyester.Other insulating materials may be used besides polyimide or polyester.Moreover, the insulator 120 does not necessarily need to be flexible;however, the flexibility is useful for fitting the optoelectronicassembly 110 into a housing (not shown), such as the housing of anoptoelectronic transmitter, receiver or transceiver. The flexibledielectric substrate 120 is coated on each side with a conductivematerial such as copper, a copper alloy, or other malleable, highlyconductive metal or metal alloy. The data signal traces 114 arefabricated from the conductive material on one side of the circuitinterconnect 104, while the entire second side of the circuitinterconnect 104 (excluding circular regions corresponding to thepositions of the signal leads 112 traversing the base of the TO packageand the anchor holes 166) serves as the ground signal conductor 116.Other methods of creating the conductive signal traces may be used as isunderstood by one skilled in the art. In an alternate embodiment, only aportion of the second side of the circuit interconnect 104 serves as theground signal conductor 116, leaving room for one or more additionalsignal traces (e.g., for power or low frequency data signals) on thesecond side of the interconnect 104. In this alternate embodiment, theground signal conductor 116 would be positioned relative to the traceson the first side of the circuit interconnect so as to provideconnections with well controlled impedance.

[0026] The side of the circuit interconnect 104 that serves as theground signal conductor 116 is depicted in FIG. 2. The small circularregions 130 represent holes in the dielectric substrate 120 of theinterconnect, through which the signal leads of the TO package extend.The annular circular regions 132 surrounding the smaller holes 130represent non-conductive, unmetalized regions in which the conductivematerial has been removed from the second side of the circuitinterconnect 104 so as to prevent electrical shorts between the signalleads and the ground signal conductor 116.

[0027] Returning to FIG. 1, the data signals are transmitted between theoptoelectronic device in the TO package 102 and electrical circuitry118. The data signal contacts 112 extend through apertures in the base124 of the TO package 102 and contact the resistors 162. For each datasignal contact 112, a separate, respective ground ring 106 surrounds thedata signal contact 112 and is attached to the base 124 of the TOpackage 102. The base 124 is a circular (actually, cylindrical) metalplate, generally held at the circuit ground voltage during operation ofthe optoelectronic device. The base 124 is the foundation of the TOpackage 102. In a preferred embodiment the base 124 is made of a metalknown as “Alloy 42,” which is an alloy of iron and nickel. In otherembodiments the base 124 may be made of other appropriate metals. Theprimary purpose of the ground rings 106 is to form a low reflectionconnection between the data signal contacts 112 and the signal traces114, so as to minimize signal reflections at the interface between thedata signal contacts 112 and the signal traces 114 (or at the interfacebetween the data signal contacts 112 and the resistors 162).

[0028]FIG. 3A shows the ground rings 106 on the back surface of the base124. The ground rings 106 are preferably highly conductive, thin metalrings that are bonded to the back, planar surface of the base 124, suchas by solder, conductive epoxy, or any other appropriate bonding orconductive attachment mechanism. As a result, the ground rings aremechanically and electrically connected to the back surface of the base124. The ground rings 106 rise slightly above the back planar surface ofthe base 124, which facilitates the bonding of the ground signalconductor 116 of the circuit interconnect 104 to the ground rings.Alternately, the ground rings 106 may be implemented as raised annularregions of the base 124, and thus as integral parts of the base. Thecircuit ground connection provided by the ground signal conductor 116,which is electrically and mechanically bonded to the ground rings 106,and possibly other portions of the base as well, keeps the entire base124 at the circuit ground voltage during normal operation. While theground rings 106 are shown in FIG. 3A as being circular or annular inshape, in other embodiments other shapes could be used. For instance,the ground rings 106 could be oval shaped structures.

[0029] Although there are two ground rings 106 surrounding the two datasignal contacts, only one ground ring is seen in FIG. 1 because of theangle of the perspective view shown in FIG. 1. The ground signalconductor 116 directly contacts the ground rings 106, and carries groundcurrent from the ground rings 106 to a circuit ground terminal 122 (FIG.1). In a preferred embodiment, the ground signal conductor 116 alsodirectly contacts the base 124 at the back surface of the TO package 102so as to provide a high quality ground connection to the entire TOpackage and the devices therein. These contacts between the groundsignal conductor 116 and the ground rings 106 and the back surface ofthe base 124 are preferably implemented by bonding these componentstogether using solder, conductive epoxy, or any other appropriatebonding or conductive attachment mechanism.

[0030] The ground signal and the data signals are maintained in a closerelationship to each other, separated by the insulator 120. Thisprovides for a controlled impedance at all frequencies in general andhigh frequencies in particular, where impedance matching is mostimportant.

[0031] Referring again to FIG. 1, the electrical circuitry 118 amplifiesand processes the electrical signals transmitted to a laser diode (theembodiment illustrated in FIG. 1B) or from a photo diode (in anotherembodiment), or both (in yet another embodiment). Thus, the electricalcircuitry 118 may include a laser driver circuit 170 (FIG. 1D), areceived signal recovery circuit, or both. Further, the electricalcircuitry 118 may include digital signal processing circuits, such asserializing circuits and deserializing circuits, and circuits thatperform data conversions, such as the 8b/10b conversion for converting adata stream into a “balanced” data stream that is balanced with respectto 1 and 0 bits, and that provides sufficient data transitions foraccurate clock and data recovery.

[0032] The electrical circuitry 118 is electrically connected to thecircuit interconnect 104. The signal traces 114 contact the electricalcircuitry 118 while the ground conductor 116 contacts the electricalcircuitry's circuit ground node 122. Elements of the electricalcircuitry 118 are typically mounted on a circuit board 168 (FIG. 1B),which is electrically connected to the signal traces 114 of the circuitinterconnect 104. In particular, output signal traces 172 on the circuitboard 168 are connected to the signal traces 114 on the circuitinterconnect 104 by solder, conductive epoxy, or any other appropriatebonding or conductive attachment mechanism. The output signal traces 172are also connected to the output of the laser driver circuit 170. Theoutput of the laser driver circuit 170 drives a laser diode housed in aTO package 102. The input to the laser driver circuit 170 is preferablycarried by two or more input signal traces 174. The input carried by theinput signal traces 174 is provided by other elements (not shown)internal and external to the electrical circuitry 118.

[0033] To avoid signal reflections and other signal degradations withinthe electrical circuitry 118, the impedances of the output and inputsignal traces 172, 174 are configured to approximately match the outputand input impedance of the laser driver circuit 170 respectively. Theoutput impedance of the laser driver circuit 170 does not, however,match the input impedance of the laser driver circuit 170. In preferredembodiments of the present invention, the input impedance of the laserdriver circuit 170 is 50 ohms and the output impedance of the laserdriver circuit 170 is 25 ohms. As a result, the impedances of the outputand input signal traces 172, 174 do not match. The widths of the outputand input signal traces 172, 174 are, however, preferably not varied forimpedance matching purposes. More specifically, the widths of the signaltraces are preferably fixed at the pad width of series and shuntcomponents connected to the signal traces (e.g., the C circuits 189, RCcircuits 190, and RLC circuits 191, 192 illustrated in FIG. 1D). This isso because varying the width of the signal traces 172, 174 or notmatching the width of the signal traces to the pad width of the seriesand shunt components creates discontinuities in the signal paths, whichcauses signal reflections and signal degradation, particularly for highfrequency signals transmitted through the signal traces 172, 174.

[0034] In order to match the impedances of the output and input signaltraces 172, 174 to the output and input impedance of the laser drivercircuit 170, without varying the widths of the output and input signaltraces, the circuit board 168 incorporates two ground planes asillustrated in FIG. 1C. As shown in FIG. 1C (not drawn to scale), afirst circuit board cross section 176 includes a signal trace (e.g.,172, 174), a first dielectric layer 180, a first ground plane 184, asecond dielectric layer 182, and a second ground plane 186. A secondcircuit board cross section 178 includes a signal trace (e.g., 172,174), a first dielectric layer 180, a second dielectric layer 182, and asecond ground plane 186. Though a first dielectric layer 180 and asecond dielectric layer 182 are separately identified in the secondcircuit board cross section 178, the first dielectric layer 180 and thesecond dielectric layer 182 effectively form a single dielectric layer.

[0035] The second circuit board cross section 178 is essentially thefirst circuit board cross section 178 with sections of the first groundplane 184 removed. More specifically, sections of the first ground plane184 are removed from (or not included in) areas of the circuit board 168close to the input signal traces 174 (the second circuit board crosssection 178 is representative of these areas). As illustrated in FIG.1C, the width of a ground plane section removed (w3) is preferablyw+2*w2, where w2 is≧3*d 2. At the very least, enough of the first groundplane 184 is removed to ensure that the first ground plane 184 does notsignificantly affect the impedance of the input signal traces 174.

[0036] The first ground plane 184, however, is not removed from (or isincluded in) areas of the circuit board 168 close to the output signaltraces 172 (the first circuit board cross section 176 is representativeof these areas). As a result, the second ground plane does not affectthe impedance of the output signal traces 172. Instead, the impedance ofthe output signal traces 172 is determined in part by the distance ofthe first ground plane 184 from the output signal traces 172.

[0037] Persons skilled in the art recognize that the characteristicimpedance of a signal trace (e.g., micro-strip transmission lines) is:$\frac{87}{\sqrt{ɛ_{r} + 1.41}}{\ln \left( \frac{5.98*h}{{0.8*w} + t} \right)}$

[0038] where ε_(r) is the dielectric constant, which varies depending onthe composition of the dielectric layer 180, 182;

[0039] where h (mils) is the distance between the signal trace and theclosest ground plane (e.g., d1 for the first circuit board cross section176 and d2 for the second circuit board cross section 178);

[0040] where w (mils) is the width of the signal trace as illustrated inFIG. 1C; and

[0041] where t (mils) is the thickness of the signal trace asillustrated in FIG. 1C.

[0042] In a preferred embodiment, the thickness of the first dielectriclayer 180 and the second dielectric layer 182 are chosen so that thecharacteristic impedance of the input signal traces 174 and thecharacteristic impedance of the output signal traces 172 are 50 ohms and25 ohms, respectively. In one embodiment of the present invention, thethickness of the first dielectric layer 180 is 5 mils and the thicknessof the second dielectric layer 182 is 8 mils. The other inputs to thecharacteristic impedance equation above are preferably the same forareas of the circuit board 168 represented by the first circuit boardcross section 176 and the second circuit board cross section 178.

[0043] In alternate embodiments, varying numbers of ground planes areincluded in areas of the circuit board 168 as needed to obtain varyingnumbers of impedances for signal traces. Additionally, such signaltraces may or may not interface with a laser driver circuit 170.

[0044]FIG. 1D illustrates components included in the laser drivercircuit 170 of a preferred embodiment. In particular, the laser drivercircuit 170 preferably includes a differential output circuit 188, two C(capacitor) circuits 189, two RC (resistor-capacitor) circuits 190, andtwo RLC (resistor-inductor-capacitor) circuits 191, 192, which areconnected to a voltage source (Vcc) and ground, respectively. The C andRC circuits 189, 190 are part of an impedance matching network that alsoincludes RLC circuits 191, 192.

[0045] The differential output circuit 188 amplifies differentialsignals from the input signal traces 174. Before being amplified by thedifferential output circuit 188, however, these differential signalspass through a corresponding C circuit 189. The C circuits 189preferably include a capacitor in series for DC blocking.

[0046] The two output signals are high frequency signals that ultimatelymodulate the output of a laser diode 402 (FIG. 4). But prior to exitingthe laser circuit 170, the first and second output signals pass througha corresponding RC circuit 190. The RC circuits 190 isolate thedifferential output circuit 188 from the RLC circuits 191, 192. Morespecifically, the RC circuits each provide a DC blocking capacitor andmatching resistor to isolate the DC level of the 188 differential outputcircuit from the RLC circuits 191, 192, which present a high impedance(e.g., an impedance that is five to ten times greater than the signaltrace impedance minimum).

[0047] The RLC circuit 191 and the RLC circuit 192 provide a biasingcurrent to a laser diode 402 in order to push the laser diode 402operating range beyond its threshold value and into a linear range. Oncein the linear range, the high frequency current provided by thedifferential output circuit 188 modulates the optical output strength ofthe laser diode 402. Preferably, the combination of elements selectedfor the RLC circuit 191 and the RLC circuit 192 are selected such thatthe voltage drop across each is minimal, yet capable of providing therequired biasing current without interfering with the high frequencycurrent provided by the differential output circuit 188.

[0048]FIG. 1E illustrates a preferred configuration of the RLC circuit191 and the RLC circuit 192. In the RLC circuit 191, a resistor 195 andan inductor 196 are connected in parallel to the output signal trace 172and to another resistor 193 and capacitor 194, which are connected inparallel to a voltage source (Vcc). And in the RLC circuit 192, aresistor 199 and an inductor 161 are connected in parallel to the outputsignal trace 172 and to another resistor 197 and capacitor 198, whichare connected in parallel to ground. Each of the resistors 193, 195,197, 199 preferably has a resistance in the range of 5 to 50 ohms. Eachof the capacitors 194, 161 preferably has a capacitance in the range of0.1 to 10 picofarads (pF). And each of the inductors 196, 198 preferablyhas an inductance in the range of 2 to 12 nanoHenries (nH).

[0049] An important aspect of the laser driver circuit 170 is how theelements included in one or more of the C circuits 189, the RC circuits190, and the RLC circuits 191, 192 are connected to signal traces 172,174. As illustrated in FIG. 1F, the pads of elements 160 (e.g.,resisters, inductors, capacitors, or other elements) are integrated intothe output signal traces 172 such that the thickness of the outputsignal traces 172 is not increased at pad junction points 159 (e.g., thelocations where the pads of elements 160 are integrated with the outputsignal traces 172). Additionally, the present invention breaks fromstandard signal trace construction by fixing the width w of the entiresignal traces to approximate the width of the signal traces at the padjunction points 159. In a preferred embodiment, the width w of theoutput signal traces 172 is 17 mils and the width w4 of the outputsignal traces 172 at the pad junction points 159 is 20 mils. Preferably,the difference between the widths w and w4 are selected so thatparasitic inductance created at pad junction points 159 is substantiallyoffset by the parasitic capacitance created at pad junction points. Inother words, the preferred configuration includes a slight increase ofthe width of the output signal traces 172 at the pad junction points159, but no more than necessary to offset any parasitic capacitancecreated at the pad junction points 159. Preferably, the width of theoutput signal traces 172 at the pad junction points 159 is not greaterthan 125% of the width of other sections of the output signal traces172.

[0050]FIG. 3A shows the base 124 at the back of the TO package 102 inone embodiment of the present invention. The signal contacts (leads) 112carrying data signals and/or a power supply voltage extend throughapertures in the base 124 of the TO package 102. The data signalcontacts 112 contact resistors 162 on the circuit interconnect 104. Thesignal contacts 112 do not contact the base 124 of the TO package 102;rather, they extend through a dielectric 140, preferably a ring ofglass, embedded in the base 124. Each dielectric ring 140 is concentricwith one of the signal contacts 112. When the circuit interconnect 104is bonded to the base of the TO package 102, the unmetalized insulatorregion 132 (FIG. 2) on the second side of the circuit interconnectoverlaps the dielectric ring 140 in the base 124. For each data signalcontact 112 (or at least each high frequency data signal contact), thereis a conductive ground ring 106 that surrounds the dielectric 140,concentric with the contact 112 and the dielectric ring 140.

[0051] In some embodiments, the ground rings 106 are the only parts ofthe TO package that directly contact the ground signal conductor 116 ofthe circuit interconnect. In one embodiment, however, the ground signalconductor 116 is mechanically and electrically bonded to a large portionof the external, back surface of the base 124, in addition to the groundrings 106. Alternatively, additional ground contacts may be provided bysignal leads connected to the TO package 102.

[0052]FIG. 3B depicts an alternate embodiment, in which a ground lug 150is used instead of the ground rings 106 to provide a high quality groundconnection to the base 124 and to prevent signal reflections in the highfrequency data signal paths. The ground lug 150 is a preferably a highlyconductive, thin metal lug bonded to the back, planar surface of thebase 124, such as by solder, conductive epoxy, or any other appropriatebonding or conductive attachment mechanism. The ground lug 150 risesabove the back planar surface of the base 124, which facilitates thebonding of the ground signal conductor 116 of the circuit interconnect104 to the ground lug. Alternately, the ground lug 150 may beimplemented as a raised region of the base 124, as an integral part ofthe base. The ground lug has two round (e.g., cylindrical) holes in it,aligned with the dielectric rings 140 surrounding the data signalcontacts 112.

[0053] The use of a ground lug, instead of ground rings, typically doesnot require any change in the design of the circuit interconnect 104. Asshown in FIG. 3B, the ground lug 150 is preferably positioned so as tosurround the data signal contacts 112. If the TO package includes morethan two high frequency data signal contacts 112, either the ground lugmay be made larger or one or more additional ground lugs 150 may bepositioned around those additional signal contacts 112 so as to providea ground current path that is precisely positioned with respect to thedata signal current flowing each of the data signal contacts 112.

[0054] The low impedance connection or bond between the ground signalconductor and the ground lug 150 is preferably formed by placing solderon the top surface of the ground lug or on the back surface of theground signal conductor 116 and then soldering the ground signalconductor 116 to the ground lug 150. Alternately, the ground signalconductor 116 may be mechanically and electrically connected to theground lug 150 using a conductive epoxy, or any other appropriateconductive attachment mechanism.

[0055] In yet another alternate embodiment, the base 124 of a TO package102 may include both ground rings and ground lugs for forming groundcurrent connections to the ground signal conductor 116 of the circuitinterconnect 104.

[0056] Referring to FIG. 4, there is shown a transmitter optoelectronicassembly 400 in accordance with an embodiment of the present invention.The transmitter optoelectronic assembly 400 includes:

[0057] a laser diode 402, such as an edge emitter or other type of laserdiode;

[0058] a laser submount 404, on which the laser diode is mounted; thelaser submount 404 may be made of aluminum nitride or alumina ceramic;the laser submount 404 preferably incorporates one or more integrated orattached passive components, such as capacitors and inductors, toprovide improved impedance matching and signal conditioning;

[0059] a laser pedestal 406 to which the submount 404 is attached; thelaser pedestal 406 is a grounded, conductive structure having apartially concentric shape with respect to data signal contacts 412, 414that extend through the base 124;

[0060] a monitor photo diode 408 for detecting the light emitted from aback facet of the laser diode 402 in order to monitor the intensity ofthe light emitted by the laser diode 402;

[0061] a monitor photo diode sub-mount 410 on which the monitor photodiode 408 is mounted; and

[0062] a Transistor Outline (TO) package 420 incorporating controlledimpedance glass-metal feedthroughs.

[0063] The partially concentric shape of the pedestal 406, which is heldat the circuit ground potential, facilitates control of the impedancecharacteristics of the circuit that runs from the data signal contacts412, 414, through bond wires 405 to the laser diode 402 and through thelaser submount 404 and laser pedestal 406 of the TO package. Inparticular, the partially concentric shape of the pedestal 406 makes thedata signal contacts 412, 414 operate as transmission lines, much likecoaxial cables. The laser pedestal may be electrically and mechanicallycoupled to the base 124 of the TO package. Alternately, the laserpedestal maybe integrally formed with the base 124 of the TO package.

[0064] The laser diode 402 is activated when a positive voltage isapplied across the p-n junction of the laser diode 402. In the preferredembodiment, data signal contacts 412, 414 form a differential datasignal connection. The two contacts 412, 414 are electrically connectedto the laser submount 404 via bond wires 405 or any another appropriateconnection mechanism. One terminal of the laser diode 402 is in directcontact with the laser submount 404 and is, therefore, electricallyconnected with one of the differential data signal contacts 414 via acorresponding one of the bond wires 405. The other data signal contact412 is electrically connected to the laser diode 402 via a bond wire 405to the submount 404 and another bond wire connecting the second terminalof the laser diode 402 to the submount 404. The differential signalprovided by data signal contacts 412, 414 supplies both a bias voltageand a time varying signal voltage across the p-n junction of the laserdiode 402.

[0065] Impedance matching within the TO package 102 may be improved byincorporating capacitors and/or inductors into the submount 404 for thelaser diode 402 to provide a network(s) (e.g., an L network, C network,or LC network) that compensates for impedance presented by the bondwires 405 between the data signal contacts 412, 414 extending throughthe TO package and the submount connection points.

[0066] Typically, the bond wires 405 are made of gold but still haveinductances of 1 to 5 nanoHenries. The inductance of the bond wires 405is a function of bond wire length. In order to minimize the length ofthe bond wires 405, therefore, the width of the submount 404 is extendedso that the length of the bond wires is minimized. FIG. 5 more clearlyillustrates that the submount 404 extends beyond the pedestal 406 toshorten the distance between the submount 404 and the data signalcontacts 412, 414. The reduced inductances of the short bond wiresreduces or eliminates the need for incorporating capacitors and/orinductors into the submount 404 for the laser diode 402. The submount404 does not create the inductances that the bond wires 404 wouldotherwise create because the submount 404 includes signal traces and aground plane 450, and thus functions as a transmission line. The signaltraces on the submount 404 are preferably configured so that theirimpedances match or approximately match the impedance of the data signalcontacts 412, 414.

[0067] As indicated above, the submount 404 includes a ground plane 450.The ground plane may be formed by the pedestal itself, or by a metallayer on the submount that is bonded to the pedestal 406. The groundplane 450 covers only the portion of the submount 404 in contact withthe pedestal 406. Because it does not extend beyond the contact areawith the pedestal 406, the ground plane 450 does not interfere with thetransmission characteristics of the data signal lines 412, 414. This isso because the partially concentric surfaces of the pedestal 406, whichis grounded, remains the closest ground “plane” to the data signal lines412, 414.

[0068] As is understood by one skilled in the art, when the laser diode402 is an edge emitter the laser diode 402 emits light in both theforward direction and the backward direction, from forward and backfacets. The forward direction refers to the direction in which light istransmitted through a window of the TO package, while the backwarddirection refers to the opposite direction. The laser intensity in thebackward direction is proportional to the laser intensity in the forwarddirection. Thus, it is useful to measure the intensity of the laser inthe backward direction in order to track the laser intensity in theforward direction. Accordingly, a monitor photo diode 408 is positionedfacing the back facet of the laser diode 402. A power supply voltagecontact 416 is connected to the monitor photo diode submount 410 by abond wire. The monitor photo diode 408 is in contact with the monitorphoto diode submount 410 and is connected to the monitor photo diodedata signal contact 418 by a bond wire. Thus, the monitor photo diode408 is reverse biased between the power supply and the data signalcontact 418. The transmitter assembly of FIG. 4 is operated inconjunction with a circuit interconnect having four data signal traces.The circuit interconnect, not shown, is preferably similar to the oneshown in FIG. 2, but having four data signal traces 114. Each datasignal trace electrically interfaces a respective one of the data signalcontacts 412, 414, 416, and 418.

[0069] Referring to FIG. 6A, there is shown an embodiment of a receiveroptoelectronic assembly 600 in accordance with the present invention.The receiver optoelectronic assembly includes:

[0070] a photo diode 602;

[0071] a photo diode submount 604;

[0072] an integrated circuit preamplifier 606 (e.g., a transimpedanceamplifier) attached to the photo diode 602 and the submount 604 via abond wire;

[0073] two bypass capacitors 608-1, 608-2;

[0074] a resistor 618; and

[0075] a Transistor Outline (TO) package 616 incorporating controlledimpedance glass-metal feedthroughs.

[0076] The photo diode 602 is positioned on the photo diode submount 604and connected to the integrated circuit preamplifier 606 and to one ofthe two bypass capacitors 608-2 via bond wires. The photo diode 602 isconfigured to turn optical data signals into electrical signals, whichare passed to, and amplified by, the integrated circuit preamplifier 606via the bond wire. The bypass capacitor 608-2 is also connected via twobond wires to a signal contact 610, which provides the photo diode 602with power. The bypass capacitor 608-2 sits atop the surface of the TOpackage 616, which is grounded. Because a bypass capacitor provides lowimpedance over certain high frequencies, high frequency noise isfiltered from the power signal transmitted by the signal contact 610before it reaches the photo diode 602.

[0077] The integrated circuit preamplifier 606 is connected to a bypasscapacitor 608-1, which is connected to a signal contact 612 thatsupplies power to the integrated circuit preamplifier 606. Like theother bypass capacitor 608-2, this bypass capacitor 608-1 sits atop thesurface of the TO package 616 and filters high frequency noise from thepower signal transmitted by the signal contact 612. The integratedcircuit preamplifier 606 transmits differential data signals throughbond wires to signal contacts 614, 620. In the embodiment illustrated inFIG. 6A, the integrated circuit preamplifier 606 includes an input stageand an output stage within the same integrated circuit. The input stagereceives data signals from the photo diode 602; the output stage outputsthe differential data signals. In this embodiment, the power signal,transmitted by the signal contact 612 through the bypass capacitor 608-1and the single bond wire to the integrated circuit preamplifier 606, isconnected internally to both the input stage and the output stage. Theground connections for the input stage and the output stage are,however, separated. Four bond wires 622 provide a connection to groundfor the output stage. Two bond wires 623 provide a ground connection forthe input stage. Separate ground connections for the input stage and theoutput stage reduces feedback gain and suppresses oscillation in theintegrated circuit preamplifier 606. In this embodiment, the grounds ofthe input stage and the output stage are connected through the groundedsurface of the TO package 616. This is, however, a more attenuatedconnection than, for example, connecting the grounds of the input stageand the output stage on the integrated circuit preamplifier 606, andthen connecting both to the surface of the TO package 616. The groundconnection for the input stage, furthermore, includes a seriesconnection to a resistor 618. The inclusion of the resistor 618 in theground connection for the input stage also reduces feedback gain andsuppresses oscillation in the integrated circuit preamplifier 606 byisolating the input stage from ground node voltage fluctuations in theoutput stage. The ground node voltage fluctuations are caused byparasitic inductance in the ground connection and correspond to currentpassing through the (parasitic) inductance of the ground connection.This phenomenon is commonly referred to as “ground bounce”.

[0078] Referring to FIG. 6B, there is shown a more detailed illustrationof the integrated circuit preamplifier 606. Included in the illustrationare a Vcc pad 650, an input stage input pad 652, a first input stageground pad 654, a second input stage ground pad 656, a first outputstage inverted output pad 658, a second output stage inverted output pad660, a first output stage ground pad 662, a second output stage groundpad 664, a third output stage ground pad 666, a fourth output stageground pad 668, a first output stage output pad 670, a second outputstage output pad 672, an input stage 676, and an output stage 678.

[0079] Briefly, the input stage 676 of the integrated circuitpreamplifier 606 receives from the photo diode 602 a current thatreflects the optical strength of a signal received by a corresponding TOpackage 102. The input stage 676 converts the current into two differentvoltage signals of equal amplitude, but 180 degrees out of phase witheach other, and applies these differential voltage signals to the outputstage 678 of the integrated circuit preamplifier 606. The output stage678 amplifies the voltage signals produced by the input stage 676 andapplies these amplified voltages to signal contacts.

[0080] In more detail now, the photo diode 602 is connected to the inputstage input pad 652 via bond wire 630—as illustrated in FIG. 6A and 6B.The input to the input stage 676 (and the output from the photo diode602) is typically a current, which the input stage 676 converts to twodifferential voltages that together reflect the magnitude of the inputcurrent. Typically, the two differential voltages are essentially equalin amplitude, but 180 degrees out of phase with each other (e.g., onemay be positive and the other negative with respect to a centervoltage).

[0081] The input stage 676 is typically an internal element so that theinput stage 676 is connected to the input stage input pad 652 via aninternal connection. FIG. 6B illustrates the internal nature of theinput stage 676 and its connection to the input stage input pad 652 withdashed lines.

[0082] Also connected to the input stage 676 via internal connectionsare the Vcc pad 650, the first input stage ground pad 654, and thesecond input stage ground pad 656 as illustrated by additional dashedlines. As indicated above, the Vcc pad 650 is connected to a signalcontact 612 for power via a bypass capacitor 608-1 and bond wires. Thefirst input stage ground pad 654 and the second input stage ground pad656 facilitate a connection between the input stage 676 and a resistor618, which is connected to ground, via bond wires 623. In oneembodiment, although not in some alternate embodiments, two or moreconnections to ground (via first input stage ground pad 654 and thesecond input stage ground pad 656) are preferably used in order toreduce inductance created by the bond wires. Persons skilled in the artrecognize that the inductance of two inductors in parallel is computedby the following${{{equation}:L_{total}} = \frac{L_{1}*L_{2}}{L_{1} + L_{2}}},$

[0083] where L_(total) is the total inductance of two bond wires inparallel and L₁ and L₂ are inductance values of a first and secondinductor respectively. If the two inductance values are equal, the totalinductance is equal to half the inductance of either bond wire alone.

[0084] Finally, input stage 676 is also connected, via connectionstypically internal to the integrated circuit preamplifier 606, to theoutput stage 678. As noted above, the output of the input stagecomprises two voltages. More specifically, the output of the input stagecomprises two voltage signals that are nominally identical in amplitude,but 180 degrees out of phase. Each of these two voltage signals isapplied to a corresponding connection or input port of the output stage678.

[0085] The output of the output stage 678 is connected to two signalcontacts 614, 620 via four pads. The output stage 678 amplifies thedifference between the two voltages from the input stage 676 and appliesthe amplified difference to the non-inverted output pads 672, 670 viatwo, separate connections that are typically internal to the integratedcircuit preamplifier 606. These two pads are, in turn, connected viabond wires to one of the two signal contacts (e.g., 614). Like theground connections described above in connection with the input stage676, dual connections to a signal contact minimize inductance created bythe connection to the signal contact.

[0086] At the same time, the output stage 678 also inverts the amplifieddifference and applies the result to the inverted output pads 658, 660via two, separate connections that are typically internal to theintegrated circuit preamplifier 606. Thus, the voltages applied to thenon-inverted output pads and the inverted output pads, respectively, arenominally identical in amplitude, but 180 degrees out of phase.Additionally, the output pads 658, 660 are connected via bond wires toone of the two signal contacts (e.g., 620). The output stage is alsoconnected to the Vcc pad 650 and four ground pads, 662, 664, 666, 668via connections typically internal to the integrated circuitpreamplifier 606. The four ground pads, 662, 664, 666, 668 are in turnconnected via separate bond wires to ground. As described in detailabove, the use of leads, which are effectively inductors, in parallelreduces the overall inductance of the ground connection.

[0087] Note that the illustration of FIG. 6B is merely an exemplarylayout of the integrated circuit preamplifier 606. The various elementsof the integrated circuit preamplifier 606 identified (e.g., input stage676 and output stage 678) are not limited to their respective size andposition shown in FIG. 6B. Additionally, persons skilled in the artrecognize that additional elements not illustrated or described hereinare typically included in circuits such as the integrated circuitpreamplifier 606.

[0088] Referring to FIG. 6C, there is shown another embodiment of areceiver optoelectronic assembly 600 in accordance with the presentinvention. The receiver optoelectronic assembly includes:

[0089] a photo diode 602;

[0090] a photo diode submount 604;

[0091] an integrated circuit preamplifier 606 (e.g., a transimpedanceamplifier) attached to the photo diode 602 and the submount 604 via abond wire;

[0092] two bypass capacitors 608-1, 608-2; and

[0093] a Transistor Outline (TO) package 616 incorporating controlledimpedance glass-metal feedthroughs.

[0094] The photo diode 602 is positioned on the photo diode submount 604and connected to the integrated circuit preamplifier 606 and to one ofthe two bypass capacitors 608-2 via bond wires. The photo diode 602 isconfigured to turn optical data signals into electrical signals, whichare passed to, and amplified by, the integrated circuit preamplifier 606via the bond wire. The bypass capacitor 608-2 is also connected via twobond wires to a signal contact 610, which provides the photo diode 602with power. The bypass capacitor 608-2 sits atop the surface of the TOpackage 616, which is grounded. Because a bypass capacitor provides lowimpedance over certain high frequencies, high frequency noise isfiltered from the power signal transmitted by the signal contact 610before it reaches the photo diode 602.

[0095] In the embodiment illustrated in FIGS. 6C and 6D, the integratedcircuit preamplifier 606 includes an input stage and an output stage.The input stage receives the electrical data signals from the photodiode 602; the output stage produces differential data signals derivedfrom the electrical data signals. The input stage and the output stageinclude separate connections 680 to a bypass capacitor 608-1, which isconnected to a signal contact 612 that supplies power to the input stageand the output stage of the integrated circuit preamplifier 606. Likethe other bypass capacitor 608-2, this bypass capacitor 608-1 filtershigh frequency noise from the power signal transmitted by the signalcontact 612. Clearly, the power pads for the input stage and the outputstage are connected via a capacitor 608-1. But because the capacitoroffers low resistance to ground for certain high frequencies, some ofthe noise that would otherwise be transmitted between the input stageand the output stage is filtered by the intervening connection to thecapacitor 608-1. The provision of separate bond wire connections 680 andpads 650, 651 for providing power to the input and output stages of thepreamplifier 606 reduces feedback gain and suppresses oscillation in theintegrated circuit preamplifier 606 by providing a small degree ofisolation of the input stage from voltage supply fluctuations in theoutput stage. As noted above, bond wires have a defined amount ofinductance. Because separate pads and bond wires are used to connect theinput stage and the output stage to the signal contact, the inductanceof the bond wires prevents feedback produced by the output stage fromentering the input stage. More specifically, when operating at, forexample, 6 GHz, a typical bond wire provides about 36 ohms of electricalisolation.

[0096] The ground connections for the input stage and the output stageare, like the power connections, separated. Four bond wires 622 providea connection to ground for the output stage. Two bond wires 623 providea ground connection for the input stage. These separate groundconnections for the input and output stages also help to provide adegree of isolation between the input stage and output stage, therebysuppressing oscillation. In this embodiment, the resistor 618 of theembodiment shown in FIG. 6B is not included. Instead, bond wires 623connect the input stage to circuit ground directly.

[0097] Referring to FIG. 6D, there is shown a more detailed illustrationof the integrated circuit preamplifier 606. Since FIGS. 6B and 6D aresimilar in most respects, only the differences between FIGS. 6B and 6Dwill be described. In particular, the integrated circuit preamplifier606 of FIG. 6D includes separate Vcc pads 650, 651 for the input stage676 and output stage 678, respectively.

[0098] It should be noted that the illustration of FIG. 6D is merely anexemplary layout of the integrated circuit preamplifier 606. The variouselements of the integrated circuit preamplifier 606 identified (e.g.,input stage 676 and output stage 678) are not limited to theirrespective size and position shown in FIG. 6D. Additionally, personsskilled in the art recognize that additional elements not illustrated ordescribed herein are typically included in circuits such as theintegrated circuit preamplifier 606.

[0099]FIG. 7 shows an embodiment of an optoelectronic transceiver 700 inaccordance with the present invention. The optoelectronic transceiver700 includes a transmitter TO package 702 and receiver TO package 704.The transmitter TO package 702 houses a light source such as a laserdiode, and the receiver TO package 704 houses a detector such as a photodiode. Data signals are transmitted from external electrical circuitry710 to the transmitter TO package 702 via the transmitter circuitinterconnect 706. The data signals from the detector are transmittedthrough the receiver TO package 704 to the external electrical circuitry710 via the receiver circuit interconnect 708. Both the transmittercircuit interconnect 706 and the receiver circuit interconnect 708ground their respective TO package through direct contact with theground rings 712 (two of which are shown in FIG. 7) surrounding the datasignal contacts 714.

[0100] While the present invention has been described with reference toa few specific embodiments, the description is illustrative of theinvention and is not to be construed as limiting the invention. Variousmodifications may occur to those skilled in the art without departingfrom the true spirit and scope of the invention as defined by theappended claims.

What is claimed is:
 1. An optoelectronic device, comprising: atransistor outline housing; a photo diode within the transistor outlinehousing; an integrated circuit, within the transistor outline housing,the integrated circuit having an input amplifier stage and an outputamplifier stage, the input amplifier stage having an input node coupledto the photo diode; the input amplifier stage configured to have aseries connection to a first resistor, said first resistor connected toa ground node; and the output amplifier stage configured to have aconnection to the ground node, said connection not overlapping theseries connection.
 2. The optoelectronic device of claim 1, wherein theresistor is within the transistor outline housing and external to theintegrated circuit.
 3. The optoelectronic device of claim 1, furthercomprising a second resistor, wherein the input amplifier stage isconfigured to have a series connection to said second resistor, saidsecond resistor connected to the ground node.
 4. The optoelectronicdevice of claim 3, wherein each conductive connection between the inputamplifier stage and the resistor and each conductive connection betweenthe resistor and the ground node is formed by a bond wire, wherein saidbond wire has an associated inductance.
 5. The optoelectronic device ofclaim 3, wherein the second resistor is within the transistor outlinehousing and external to the integrated circuit.
 6. The optoelectronicdevice of claim 1, further comprising a plurality of additionalconnections between the ground node and the output amplifier stage, eachof said plurality of additional connections formed by a bond wire,wherein said bond wire is connected to both said ground node and saidoutput amplifier stage, wherein said bond wire has an associatedinductance.
 7. The optoelectronic device of claim 1, further comprisingan output node, wherein the output amplifier stage is coupled to asignal contact through said output node.
 8. The optoelectronic device ofclaim 1, further comprising one or more additional output nodes, whereineach of said one or more additional output nodes connects the outputamplifier stage to one of the signal contact and a second signalcontact; and at least one of said one or more additional output nodes isconnected to the second signal contact.
 9. The optoelectronic device ofclaim 8, wherein each conductive connection between the output amplifierstage and the signal contact and each conductive connection between theoutput amplifier stage and the second signal contact is formed by a bondwire, wherein said bond wire has an associated inductance.
 10. Theoptoelectronic device of claim 1, wherein the input amplifier stage andthe output amplifier stage are connected to a voltage source pad, saidvoltage source pad connected by one or more bond wires to voltage sourcewithin the transistor outline housing, wherein each of said one or morebond wires has an associated inductance.
 11. An optoelectronic device,comprising: a transistor outline housing; a photo diode within thetransistor outline housing; an integrated circuit, within the transistoroutline housing, the integrated circuit having an input amplifier stageand an output amplifier stage, the input amplifier stage having an inputnode coupled to the photo diode; the input stage configured to have afirst connection to a capacitor, said capacitor connected to a groundnode and a power source; and the output stage configured to have asecond connection to the capacitor, whereby a defined range of highfrequencies are prevented by said capacitor from flowing between theinput stage and said output stage via a connection to the power source.12. The optoelectronic device of claim 11, wherein the first connectionincludes a first bond wire and the second connection includes a secondbond wire; wherein the first bond wire and second bond wire each havingan associated inductance.
 13. The optoelectronic device of claim 1,wherein the input amplifier stage is configured to have one or moreconductive connections to the ground node.
 14. The optoelectronic deviceof claim 13, wherein each of said one or more conductive connectionsbetween the input amplifier stage and the ground node is formed by abond wire, wherein said bond wire has an associated inductance.
 15. Theoptoelectronic device of claim 13, wherein the output amplifier stageconfigured to have one or more conductive connections to the groundnode, said one or more conductive connections not overlapping the one ormore conductive connections between the input amplifier stage and saidground node, said one or more conductive connections between the outputamplifier stage and the ground node formed by a bond wire, wherein saidbond wire has an associated inductance.
 16. The optoelectronic device ofclaim 11, further comprising an output node, wherein the outputamplifier stage is coupled to a signal contact through said output node.17. The optoelectronic device of claim 16, further comprising one ormore additional output nodes, wherein each of said one or moreadditional output nodes connects the output amplifier stage to one ofthe signal contact and a second signal contact; and at least one of saidone or more additional output nodes is connected to the second signalcontact.
 18. The optoelectronic device of claim 17, wherein eachconductive connection between the output amplifier stage and the signalcontact and each conductive connection between the output amplifierstage and the second signal contact is formed by a bond wire, whereinsaid bond wire has an associated inductance.